That morning at around 8:15 a.m., a patient coming in for a scheduled appointment found Rainey, 54, on the floor of his office with his jaw crushed and teeth smashed in, police said.

LAPD detectives believe he was killed sometime between 7 and 8 a.m., and are now combing through surveillance footage from the area -- although not all of the cameras were operational at the time of the murder, NBC reports.

Meanwhile, Rainey’s brother, L.A. Times media writer Jim Rainey, has written a moving tribute to his brother which he posted on his Facebook page.

In it he gave details on his brother’s life, accomplishments and character -- describing him, for example, as a wine connoisseur and “something of a health nut.”

An avid runner, Rainey was well-known and very active among long-distance running groups such as the Santa Monica Mountain Goats, Jim Rainey said.

“Our father, Ford Rainey, lived to two weeks shy of his 97th birthday. Robert told people he would live longer. At first he said he was shooting for 100. At some point he moved his target to 105. Recently, he recalibrated again: 110 didn’t seem unreasonable.”

He was also a friend to disadvantaged people, and “would talk to every oddball door-to-door salesman who came by his office. He would give handouts to the homeless men who hung out in the neighborhood. Sometimes he would pay them for an odd job.”

Above all, Jim Rainey wrote, “Robert Rainey was a gentle man. He didn’t pick fights or look for trouble. He had a kind heart. ... He deserved a much better, more humane end.”

Anyone with potential information on Robert Rainey’s murder is urged to call LAPD West Bureau homicide detectives at (213) 382-9470. The office where he was found, Rainey Chiropractic, is located on the second floor of a strip mall on the 9200 block of Venice Boulevard in Palms, just over the border from Culver City.

Authorities sometimes ask that business owners keep their surveillance equipment operational as it can help them solve crimes. As LAPD Det. Glenn O’Shea told KPCC in April, “Make sure your video functions.”